Coal ash treatment method and apparatus

Abstract

To effectively utilize coal ash while reducing mercury concentration in cement kiln exhaust gas. Coal ash is received from a thermal power plant or the like; the received coal ash is separated into ash and unburned carbon; the separated ash is utilized in a cement manufacturing facility as a cement raw material; and the separated unburned carbon is utilized in the cement manufacturing facility in accordance with mercury concentration in gas exhausted from a cement kiln of the cement manufacturing facility. In case that the mercury concentration in the gas exhausted from the cement kiln of the cement manufacturing facility is high, in the coal ash, unburned carbon with high mercury content can be treated in facilities other than the cement manufacturing facility without feeding the unburned carbon to the cement manufacturing facility, or the quantity of such unburned carbon fed to the cement manufacturing facility can be adjusted. It is possible to separate mercury from the separated unburned carbon, and utilize the unburned carbon from which mercury is separated in the cement manufacturing facility as a fuel.

The invention claimed is: 
     
       1. A method of treating coal ash comprising the steps of:
 receiving coal ash at a cement manufacturing facility; 
 separating the received coal ash into ash and unburned carbon; 
 utilizing the separated ash in the cement manufacturing facility as a cement raw material; 
 feeding the separated unburned carbon into the cement manufacturing facility, wherein the separated unburned carbon is used in the cement manufacturing facility as a fuel; 
 determining the mercury level in the cement kiln exhaust gas; 
 adjusting the feed rate of the unburned carbon used as a fuel to the cement manufacturing facility in accordance with the mercury level in the cement kiln exhaust gas, wherein the feed rate of unburned carbon is increased as the mercury level decreases and the feed rate of unburned carbon is decreased as the mercury level increases. 
 
     
     
       2. The method of treating coal ash as claimed in  claim 1 , wherein mercury is separated from said separated unburned carbon, and the unburned carbon from which the mercury is separated is utilized in the cement manufacturing facility as a fuel. 
     
     
       3. The method of treating coal ash as claimed in  claim 1 , wherein said coal ash is separated into the ash and the unburned carbon by an electrostatic method or a flotation method. 
     
     
       4. The method of treating coal ash as claimed in  claim 1 , wherein said mercury is separated from the separated unburned carbon by thermal desorption with inactive gas or elution separation with oxidant. 
     
     
       5. The method of treating coal ash as claimed in  claim 1 , wherein said unburned carbon from which mercury is separated is utilized as a fuel for a cement kiln or a fuel for drying coal ash after wet decarbonization. 
     
     
       6. The method of treating coal ash as claimed in  claim 1 , further comprising the step of adsorbing the mercury removed from the unburned carbon to ionic exchange resin or solidifying the mercury by oxidization so as to be rematerialized in refineries. 
     
     
       7. The method of treating coal ash as claimed in  claim 2 , wherein said coal ash is separated into the ash and the unburned carbon by an electrostatic method or a flotation method. 
     
     
       8. The method of treating coal ash as claimed in  claim 2 , wherein said mercury is separated from the separated unburned carbon by thermal desorption with inactive gas or elution separation with oxidant. 
     
     
       9. The method of treating coal ash as claimed in  claim 3 , wherein said mercury is separated from the separated unburned carbon by thermal desorption with inactive gas or elution separation with oxidant. 
     
     
       10. The method of treating coal ash as claimed in  claim 2 , wherein said unburned carbon from which mercury is separated is utilized as a fuel for a cement kiln or a fuel for drying coal ash after wet decarbonization. 
     
     
       11. The method of treating coal ash as claimed in  claim 3 , wherein said unburned carbon from which mercury is separated is utilized as a fuel for a cement kiln or a fuel for drying coal ash after wet decarbonization. 
     
     
       12. The method of treating coal ash as claimed in  claim 4 , wherein said unburned carbon from which mercury is separated is utilized as a fuel for a cement kiln or a fuel for drying coal ash after wet decarbonization. 
     
     
       13. The method of treating coal ash as claimed in  claim 2 , further comprising the step of adsorbing the mercury removed from the unburned carbon to ionic exchange resin or solidifying the mercury by oxidation so as to be rematerialized in refineries. 
     
     
       14. The method of treating coal ash as claimed in  claim 3 , further comprising the step of adsorbing the mercury removed from the unburned carbon to ionic exchange resin or solidifying the mercury by oxidization so as to be rematerialized in refineries. 
     
     
       15. The method of treating coal ash as claimed in  claim 4 , further comprising the step of adsorbing the mercury removed from the unburned carbon to ionic exchange resin or solidifying the mercury by oxidization so as to be rematerialized in refineries. 
     
     
       16. The method of treating coal ash a claimed in  claim 5 , further comprising the step of adsorbing the mercury removed from the unburned carbon to ionic exchange resin or solidifying the mercury by oxidization so as to be rematerialized in refineries. 
     
     
       17. The method of treating coal ash as claimed in  claim 1 , wherein the adjusting step is performed to prevent mercury concentration in the cement kiln exhaust gas from increasing. 
     
     
       18. The method of treating coal ash as claimed in  claim 1 , wherein the monitoring step includes measuring the mercury levels in the cement kiln exhaust gas. 
     
     
       19. A method of treating coal ash comprising the steps of:
 receiving coal ash at a cement manufacturing facility; 
 separating the received coal ash into ash and unburned carbon; 
 utilizing the separated ash in the cement manufacturing facility as a cement raw material; 
 feeding the separated unburned carbon into the cement manufacturing facility; and 
 adjusting the feed rate of the unburned carbon to the cement manufacturing facility in accordance with the mercury level in the cement kiln exhaust gas, wherein the feed rate of unburned carbon is increased as the mercury level decreases and the feed rate of unburned carbon is decreased as the mercury level increaes.